Selecting an appropriate, effective euthanasia agent is controversial. Several recent publications provide clarity on the use of CO₂ in laboratory rats and mice. This review examines previous studies on CO₂ euthanasia and presents the current body of knowledge on the subject. Potential areas for further investigation and recommendations are provided.

The targeted use of animals in teaching at institutions of higher learning is fundamental to educating the next generation of professionals in the biologic and animal sciences. As with animal research, universities and colleges that use animals in teaching are subject to regulatory oversight. Instructors must receive approval from their IACUC before using animals in their teaching. However, the questions asked on many institutions' animal care and use protocol (ACUP) are often geared more toward the use of animals for research. These questions may not be wholly appropriate in evaluating a teaching protocol; some questions are not applicable (for example, power analysis to justify animal numbers) whereas other important questions may be missing. This article discusses the issues surrounding the rationale for animal use in teaching; it also proposes a framework that instructors and IACUC members alike can use when writing and reviewing teaching ACUP. We hope this framework will help to ensure the most appropriate IACUC review of the ethical use of animals in higher education.

Chimpanzees are the closest phylogenetic relatives to humans, sharing more than 98% genetic sequence identity. These genetic similarities prompted the belief that chimpanzees can serve as an ideal model for human disease conditions and vaccine development. However, in light of the recent NIH decision to phase out biomedical research in chimpanzees and retire NIH-supported chimpanzees, data from the present study will continue to provide value for the care of aged and sick chimpanzees located in zoos, sanctuaries, and primate centers. Surprisingly little information has been published regarding the normal chimpanzee immune system, and most extant studies have been based on small numbers of animals. In the current study, we provide a better understanding of the chimpanzee immune system with regard to age and sex. We examined immune parameters of chimpanzees (n = 94; 51 female, 43 male; age, 6 to 47 y) by using flow cytometry, immune function analysis, and cytokine analysis. Because lymphocytes are key mediators of cellular immune responses, particularly to intracellular pathogens such as viruses, we surveyed the phenotypic and functional attributes of T and B lymphocytes in this healthy and age-stratified population of chimpanzees. We noted a significantly higher percentage of CD16⁺T cells in male compared with female chimpanzees but no significant changes in percentages of CD3⁺, CD4⁺, CD8⁺, or CD4⁺CD8⁺ T cells with age or sex. In addition, aging was associated with decreased proliferative responses to mitogens in both sexes. Sex-specific differences also were present in the percentage of NK cells but not in their cytotoxic activity and in circulating cytokine levels in plasma. Going forward, the data presented here regarding immune cell changes associated with aging in healthy chimpanzees will serve to enhance the care of geriatric and ill animals.

Because rhesus macaques (Macaca mulatta) are prolific breeders, overpopulation can be problematic in both research and feral populations. Currently, the most effective contraceptive methods are hormonal control in female macaques and vasectomies in males. These methods each come with innate challenges, the foremost being the alteration of necessary hormonal patterns. In this study, we assessed the use of zinc gluconate neutralized with arginine as a novel, nonsurgical alternative to male contraception in 12 rhesus macaques. This FDA-approved product for dogs is given as a one-time, intratesticular injection to cause permanent infertility yet theoretically spare the testosterone-producing Leydig cells of the testis. CBC counts, serum biochemistry analyses, testosterone levels, and testicular widths were evaluated at the time of injection and at 1 wk, 1 mo, 2 mo, or 3 mo afterward. Daily postinjection observations revealed transient scrotal enlargement in 8 of the 12 macaques but no indications of pain. In addition, full necropsies including testicular histopathology were assessed at study endpoints. Although some portion of every testis had evidence of seminiferous tubule loss, normal spermatogenesis was present in 22 of the 24 testes. In conclusion, chemical castration with the tested zinc gluconate neutralized with arginine product is not an effective method for sterilization of male rhesus macaques.

Control of rodent adventitial infections in biomedical research facilities is of extreme importance in assuring both animal welfare and high-quality research results. Sixty-three U.S. institutions participated in a survey reporting the methods used to detect and control these infections and the prevalence of outbreaks from 1 January 2014 through 31 December 2015. These results were then compared with the results of 2 similar surveys published in 1998 and 2008. The results of the current survey demonstrated that the rate of viral outbreaks in mouse colonies was decreasing, particularly in barrier facilities, whereas the prevalence of parasitic outbreaks has remained constant. These results will help our profession focus its efforts in the control of adventitial rodent disease outbreaks to the areas of the greatest needs.

Mice undergo a variety of procedures that necessitate the use of analgesic agents. Opioids are often essential to successful pain management plans, but most are controlled substances, and their use requires appropriate federal and state registrations. Nalbuphine is a potentially effective opioid analgesic for mice that is not currently classified as a controlled substance. This compound has received little attention as an analgesic for mice, and standard dosage regimens have not been developed. Here we compared the pharmacokinetic profiles of 10 mg/kg nalbuphine in male C57BL/6 mice subcutaneous or intraperitoneal administration. Blood was collected from 3 mice per treatment at 5, 10, 20, and 30 min and 1, 2, 3, 6, 12, and 24 h after administration. Plasma concentrations were measured, and standard pharmacokinetic parameters were calculated. Profile characteristics for each route of administration were similar, with significant differences in plasma concentration at 5 and 30 min and 1 and 3 h. Nalbuphine was absorbed more quickly when administered subcutaneously (T_max, 5 min) than intraperitoneally (T_max, 10 min), whereas the drug's half-life was similar between the intraperitoneal (0.94 h) and subcutaneous (1.12 h) routes. The AUC_0-tldc and AUC_0-inf were higher but the apparent clearance and apparent volume of distribution were lower after subcutaneous administration compared with intraperitoneal dosing. Plasma concentrations were below the level of detection by 12 h. These results suggest that nalbuphine is absorbed in and eliminated quickly from mice, making it a possible candidate for acute pain management.

This study evaluated the pharmacokinetic profile of a single dose of meloxicam (1.0 mg/kg) administered subcutaneously (n = 6) or intravenously (n = 2) to black-tailed prairie dogs (Cynomys ludovicianus). Blood was collected immediately before (time 0) and at 0.5, 1, 2, 4, 8, 12 and 24 h after drug administration. Plasma meloxicam concentrations were quantified with HPLC–mass spectrometry, and noncompartmental pharmacokinetic analysis was performed. The peak plasma concentrations, time to peak plasma concentration, and terminal half-life of meloxicam after subcutaneous administration (median [minimum–maximum]) were 4.30 (3.00–4.89) μg/mL, 2.00 (0.62–4.00) h, and 11.88 (7.35–18.64) h, respectively. Plasma concentrations of meloxicam for prairie dogs in the present study showed high absorption and slow elimination after drug administration. The results of this study suggest that a 1.0-mg/kg SC dose of meloxicam administered every 24 h might be excessive for prairie dogs, although the ideal therapeutic dose in terms of safety and efficacy is unknown in this species.

Gray short-tailed opossums are used in a wide variety of research in the areas of developmental biology, oncology, immunology, and comparative biology. Despite many frequent experimental manipulations of these animals under anesthesia, few studies to date have characterized the effects of anesthesia in this species. Our aim was to identify safe and effective injectable anesthetic combinations using ketamine and xylazine or ketamine and dexmedetomidine at doses of 40 mg/kg to 100 mg/kg for ketamine, 5 mg/kg to 10 mg/kg for xylazine, and 0.05 mg/kg to 0.1 mg/kg for dexmedetomidine. Effects of the proposed regimens ranged from light sedation to surgical anesthesia, but only 100 mg/kg ketamine + 0.1 mg/kg dexmedetomidine induced surgical anesthesia in all opossums, with a mean duration of 25.4 min. The 2 lowest doses of ketamine and xylazine (40 mg/kg ketamine + 5 mg/kg xylazine and 40 mg/kg ketamine + 10 mg/kg xylazine) achieved sedation to light anesthesia in all animals but did not produce a surgical plane of anesthesia in any animal. All regimens that induced a surgical plane of anesthesia caused bradycardia and bradypnea, and 75 mg/kg ketamine + 10 mg/kg xylazine and 100 mg/kg ketamine + 0.1 mg/kg dexmedetomidine caused the greatest decreases in SpO₂. Except for one opossum that died of unknown causes, all animals remained healthy and apparently free of anesthetic complications. Among all treatments, isoflurane delivered by a precision vaporizer provided the most consistent and reliable anesthesia; therefore, we recommend inhalant anesthesia over the injectable combinations used in this study.

Sheep used as surgical models require appropriate pain management, and the commonly used transdermal fentanyl patches require a long predosing period to achieve adequate plasma concentrations. The aim of this study was to assess the pharmacokinetic parameters of an FDA-approved transdermal fentanyl solution (TFS) that has yet to be tested in sheep. In this study, we compared TFS at 2.7 mg/kg (n = 2), 1.7 mg/kg (n = 3), and 0.5 mg/kg (n = 3) with the control fentanyl patch at 2 μg/kg/h (n = 1); both products were applied topically to the intrascapular region. Plasma concentrations showed significant interanimal variability. Severe adverse effects occurred at both 2.7 and 1.7 mg/kg TFS and mild to moderate adverse effects were noted at 0.5 mg/kg. At all 3 doses, TFS had greater maximal concentration, clearance rate, and volume of distribution; shorter time to maximal concentration; and similar half-lives to those of the patch. In addition, we validated the use of a commercial human fentanyl ELISA kit, which positively correlated with the liquid chromatography–mass spectroscopy data, but absolute values did not match. Overall, at all 3 dosages tested (0.5, 1.7, and 2.7 mg/kg), TFS delivered fentanyl plasma concentrations that exceeded the minimal effective concentration; however, adverse effects were noted at all 3 dosages. Caution and further study are required before the use of TFS in sheep can be recommended fully.

Because of its extended half-life, cefovecin is a broad-spectrum cephalosporin antibiotic commonly used to treat dermatitis in dogs and cats. A single injection in dogs can yield an effective plasma concentration for as long as 14 d, depending on the strain of Staphylococcus and for as long as 7 d in cats for the treatment of Pasteurella multocida. In the laboratory animal setting, C57BL/6 mice are commonly affected with dermatologic conditions that make these animals unsuitable for experiments. Therefore, we performed this pharmacokinetic study to determine whether cefovecin would be of benefit in mice. Plasma levels of the drug were determined by HPLC. For this study, single-bolus subcutaneous dosages of 8 and 40 mg/kg were assessed. The results showed that the dosage of 40 mg/kg achieved a maximal plasma concentration of 411.54 μg/mL with a half-life of 0.84 h, whereas 8 mg/kg yielded 78.18 μg/mL and 1.07 h respectively. The pharmacokinetic results suggest that cefovecin is not suitable as a long-acting antibiotic after a single subcutaneous bolus injection in mice for the treatment of dermatitis or any other bacteria sensitive to this medication.

Laboratory mice (Mus musculus) are prone to develop hypothermia during anesthesia for surgery, thus potentially impeding anesthetic recovery, wound healing, and future health. The core body temperatures of isoflurane-anesthetized mice are influenced by the choice of supplemental heat sources; however, the contribution of various surgical scrubs on the body temperatures of mice under gas anesthesia has not been assessed. We sought to quantify the effect of using alcohol (70% isopropyl alcohol [IPA]) compared with saline to rinse away surgical scrub on the progression of hypothermia in anesthetized mice (n = 47). IPA, room-temperature saline, or warmed saline (37 °C) was combined with povidone–iodine and then assessed for effects on core (rectal) and surface (infrared) temperatures. Agents were applied to a 2×2-cm shaved abdominal area of mice maintained on a water-recirculating blanket (at 38 °C) under isoflurane anesthesia (1.5% to 2.0% at 0.6 L/min) for 30 min. Although all scrub regimens significantly decreased body temperature at the time of application, treatments that included povidone–iodine led to the coldest core temperatures, which persisted while mice were anesthetized. Compared with room-temperature saline and when combined with povidone–iodine, warming of saline did not ameliorate heat loss. IPA alone demonstrated the most dramatic cooling of both surface and core readings at application but generated an unanticipated warming (rebound) phase during which body temperatures equilibrated with those of controls within minutes of application. Although alcohol is inappropriate as a stand-alone agent for surgical skin preparation, IPA is a viable alternative to saline-based rinses in this context, and its use should be encouraged within institutional guidance for rodent surgical procedures without concern for prolonged hypothermia in mice.

Various animal models are indispensible in biomedical research. Increasing awareness and regulations have prompted the adaptation of more humane approaches in the use of laboratory animals. With the development of easier and faster methodologies to generate genetically altered animals, convenient and humane methods to genotype these animals are important for research involving such animals. Here, we report skin swabbing as a simple and noninvasive method for extracting genomic DNA from mice and frogs for genotyping. We show that this method is highly reliable and suitable for both immature and adult animals. Our approach allows a simpler and more humane approach for genotyping vertebrate animals.